The objective of this study is to search for some reliable urinary biochemical profile representative of stone forming and potential stone forming patients. Much laboratory data has been accumulated relative to the presence of urinary inhibitors of crystallization in metastable solutions but this has not proven to have more than a very limited application in identifying potential stone formers or in preventing calcigerous stone formation. The identification of specific urinary macromolecules in the urine of stone forming patients will enhance our knowledge of the process of stone initiation and growth that may have practical application in providing guidelines to prevent crystal-matrix aggregation. Twenty-four hour urine specimens will be obtained from metabolically active calcium oxalate and/or calcium phosphate stone forming patients, a non-stone forming control population and a group of patients predisposed to stone disease (non-affected brothers of stone formers). Urinary macromolecule (M.W. 50,000-1,000) will be concentrated by ultrafiltration and separated by sephadex column chromatography. Each fraction will be analyzed for calcium binding activity, effect on seeded crystal growth and immunological reactivity to anti-stone matrix antibody. It is anticipated that specific macromolecular components will be identified in stone urine that are absent in normal urine. These macromolecules may serve as a useful measure in evaluating patients predisposed to stone disease.